Cocoa butter is a natural fat derived by hydraulic or expeller pressing or by solvent extraction of cocoa beans. The unique melting behavior of cocoa butter makes it highly desirable for use in chocolate and similar food products. Unlike other triglycerides obtained from natural sources, cocoa butter exhibits a distinct brittle fracture below 20.degree. C. (68.degree. F.), a fairly sharp and complete melting point at about 35.degree. C. (95.degree. F.) with an incipient fusion or softening around 30.degree.-32.degree. C. (86.degree.-90.degree. F.). A chocolate product comprising cocoa butter thus is solid at room temperature but when consumed melts rapidly at body temperature to provide excellent non-waxy mouthfeel and consistency.
The unique physical properties of cocoa butter are attributable to the particular combination and positional distribution of fatty acid acyl groups on the three carbons of glycerol. Cocoa butter contains approximately equimolar proportions of three major fatty acid acyl groups (palmitate, stearate, oleate), but only three major molecular species despite the possibility of many additional combinations of the dominant fatty acids. Apparently the enzymes present in the maturing cocoa beans are capable of selectively producing these major species.
As natural cocoa butter is relatively expensive compared to other more readily available lipids, considerable effort has been devoted to developing economical processes for synthesizing triglycerides having melting properties analogous to cocoa butter. This objective has proven to be quite difficult to accomplish owing to the inability of conventional esterification methods to position the necessary fatty acid acyl groups regioselectively (i.e., at particular carbon atoms of the glycerol).
The processing of cocoa butter into acceptable confectionary products is complicated by the fact that cocoa butter can exist in several different crystalline forms. As certain of these crystalline forms are unstable, products containing cocoa butter must be carefully tempered and/or seeded to give a smooth crystalline solid of the desired firmness and mouthfeel which will keep satisfactorily without discoloration or bloom.
Another disadvantage of cocoa butter is its high caloric content. Although the chemical composition of cocoa butter is distinctly different from that of other natural oils and fats, it is metabolized in an analogous manner and thus contributes substantially to the energy value of a food composition. Because of the desire of many persons to limit their caloric intake for reasons of health or fitness, a cocoa butter substitute having the same melting properties as natural cocoa butter but fewer calories would be of considerable value.
Certain sucrose fatty acid esters have been proposed for use as reduced calorie cocoa butter substitutes, as described, for example, in U.S. Pat. No. 4,872,875 (McCoy et al.) and European Pat. Publication No. 350,981 (Castenmiller et al.).
Reduced calorie food compositions containing fat-type organoleptic ingredients are also known wherein an esterified epoxide-extended polyol is employed as a full or partial replacement for vegetable oils and fats. Fat substitutes of this type are disclosed in U.S. Pat. No. 4,861,613 (White et al.). However, it has not heretofore been known how to modify and adapt such substances so as to render them suitable for use as cocoa butter replacements.